1. Field of the Invention
The present invention relates generally to a presensitized planographic plate which does not require a fountain solution (hereinafter, such a planographic plate is designated a "dry presensitized planographic plate"). More particularly, the invention relates to a dry presensitized planographic plate having coated on a support a layer comprising a photosensitive azide compound and a silicone rubber.
2. Description of the Prior Art
A dry presensitized planographic plate which utilizes the printing ink-repellency of a silicone rubber is known. Such a dry presensitized planographic plate has a layer of a photosensitive material and a layer of silicone rubber as separate layers as described in detail in, for instance, the specifications of U.S. Pat. Nos. 3,677,178 and 3,511,178.
However, such a conventional dry presensitized planographic plate has the following problems:
1. Since the dry presensitized planographic plate has a so-called multi-layer structure composed of a layer of the photosensitive material and a layer of the silicon rubber, it is important to adhere both layers closely and strongly on preparation of the planographic plate.
2. In a type of dry planographic plate in which the uppermost layer is a silicone rubber layer, the uppermost layer is restricted in thickness to permit permeation of a developer through the layer.
3. In a type of dry planographic plate wherein a photo sensitive layer is disposed on a silicone rubber layer, a temporary support is additionally required and also the adhesive property of the photosensitive layer to the silicone rubber is not very good.